Lithium electrochemical deintercalation from O2-LiCoO2: Structure and physical properties

• Published in: Journal of the Electrochemical Society Vol. 149; no. 10; pp. A1310 - A1320
• Main Authors: CARLIER, D, SAADOUNE, I, MENETRIER, M, DELMAS, C
• Format: Journal Article
• Language: English
• Published: Pennington, NJ Electrochemical Society 2002
• Subjects: Applied sciences; Chemical Sciences; Direct energy conversion and energy accumulation; Electrical engineering. Electrical power engineering; Electrical power engineering; Electrochemical conversion: primary and secondary batteries, fuel cells; Exact sciences and technology; Material chemistry; Cobalt oxide; Ternary compound; Alkali metal Compounds; Crystalline phase; Electronic properties; Transition metal Compounds; Secondary cell; NMR spectrometry; Electrode material; Electric batteries; Lattice parameters; X ray diffraction; Discharge charge cycle; Intercalation compound; Metal metal oxide batteries; Lithium 7; Organic electrolyte storage battery; Lithium oxide; Crystal morphology; Specific capacity; Electrical characteristic; Lithium
• ISSN: 0013-4651; 1945-7111
• DOI: 10.1149/1.1503075

Electrochemical deintercalation of Li from the metastable O2-LiCoO2 phase has been investigated up to the composition Li0.15CoO2. The single-phase domains that separate the voltage plateaus observed have been characterized by X-ray diffraction. The succession of phases observed upon deintercalation results from reversible sheet gliding or lithium/vacancy ordering, leading to the sequence 02, T#2, T#2', 06, 02, 02. In particular, the T#2 stacking, similar to the T2 phase reported by Dahn and co-workers for the Li2/3Ni1/3Mn2/3O2 phases, corresponds to oxygen ions not sitting on the three positions of a triangular lattice, hence the # character is used. It exhibits very distorted tetrahedral sites for Li. The 06 stacking exhibits two kinds of CoO6 octahedra, which might allow Co3+/Co4+ ordering in alternate sheets. The most deintercalated O2-Li0.15CoO2 phase has never been reported before. Electronic properties and 7Li magic-angle spinning nuclear magnetic resonance show a transition to a metallic state for x< 0.94 (appearance of the T#2 phase with x = 0.72). These stacking changes are proposed to result from the minimization of electrostatic repulsion, except for T#2' (x = 0.50), which is believed to result from a Li/vacancy ordering.